MP is quite scarce, making it a good default option whenever you are offered a choice.

Your total MP also determines your MP recovery rate after each fight. A character gets 1MP for each 20 MP total stat per fight. For instance: with a total MP of 70, that character gains 3MP after the fight. Add a trinket I (+10MP total, thus 80), you'd get 4MP post battle. For 8 MP recovery, you need MP between 160-179 total MP, including all gear.

SPD is essential: it allows you to act faster, which means not only more attacks than the enemies but also attacking before the enemies can inflict damage and status effects on you. You may even stun them so that they cannot even attack you.

ATK is important for all characters. MAG is crucial for your healer/elementarist (two classes worth combining).

On Normal difficulty, some of the high-end mobs (like Highguard or Skywind) have monster-specific Stat potions for stealing/dropping. While most of them have a very low (only 1% or so) chance for those potions, Highguard has a much better (maybe 10%) chance to drop Stat ATK potions. Do not miss the opportunity to Steal/Pilfer 3-4 times if you encounter a Highguard!